KR19980019378A - Fabrication Method of Simple Beam Pre-Flex Composite Beam Using Branch Point - Google Patents

Abstract

In the manufacturing method of the existing simple beam type preflex composite beam, the lower casing concrete is poured and cured under the condition of preflex load, and then released. The beam is placed between the shifts, and an additional branch point is installed at the center of the branch. After raising and casting the upper casing concrete and lowering the branch point, the compressive stress can be introduced to the lower casing concrete to introduce more compressive stress than the manufacturing method of the existing simple beam preflex composite beam. Manufacturing method of simple beam preprex composite beam using branch point to reduce quantity.

Description

Fabrication Method of Simple Beam Pre-Flex Composite Beam Using Branch Point

The existing simple beam preflex composite beam has a phenomenon in which the compressive stress introduced into the lower casing concrete decreases due to the initial creep and dry shrinkage, and thus the branch beam which is a manufacturing method of the simple beam preflex composite beam using the branch point according to the present invention. By using it, additional compressive stress can be introduced and it can be designed with smaller cross section than the existing cross section.

In the present invention, the conventional simple beam preflex composite beams are fabricated by dead and live loads by introducing additional compressive stresses by increasing and decreasing branch points installed in the middle of the reduction of compressive stress caused by creep and dry shrinkage. Tensile stress can be reduced.

1 is a manufacturing principle diagram of a conventional simple beam preflex composite beam

Figure 2 is a principle diagram for introducing an additional compressive stress by prestressing the tension material to the existing simple beam preflex composite beam

Figure 3 is a manufacturing principle diagram of a simple beam preflex composite beam using a branch point according to the present invention

4 is a) cross-sectional value when the lower casing concrete is poured in the state of loading the preflexion load in the simple beam type preplex composite beam using the branch point according to the present invention;

B) The cross-sectional value when the upper casing concrete and the abdominal concrete are poured after the branch point is raised in the simple beam preflex composite beam using the branch point according to the present invention.

5 is a) cross-sectional specifications and final stress of the simple beam-type preflex composite beam using the branch point according to the present invention

B) Sectional specifications and final stress diagrams of conventional simple beam preflex composite beams

The conventional simple beam preplex composite beam has been widely constructed so far because of its advantages such as quickness of construction, high mold reduction, improvement of material hooking and fatigue fracture strength. The conventional simple beam preflex composite beam is manufactured by bending the steel I-shaped beam to the upper part of the central part and then placing and curing casing concrete on the lower flange of the steel while applying a preflection load downward within the elastic range of the material. Then, by removing the preflection load, the compressive stress is introduced into the lower casing concrete to reduce the tensile stress of the lower flange portion caused by dead and live loads (see Fig. 1). In the process of refining and curing the lower casing concrete in the state of loading, the compressive stress is primarily reduced by creep and dry shrinkage.

Therefore, in order to prevent the reduction of the compressive stress, a method of introducing additional compressive stress using a tension member is used, but it is not only cumbersome in manufacturing but also additional costs such as tensioning the tension member (see FIG. 2). As a method for solving problems such as loss of compressive stress in the conventional simple beam type preplex composite beam, the present invention has developed a method for manufacturing a simple beam type preplex composite beam using branch points. Looking at the procedure of the manufacturing method of the simple beam preprex composite beam using the branch point according to the present invention.

3 (a) is a state diagram in which a branch point is installed at the center of the bridge by placing the lower casing concrete in a state in which the preflex load is loaded and curing the same as in the conventional simple beam preflex composite beam. 3 (b) is a state diagram in which the upper casing concrete and the abdominal concrete are poured and cured in a state where the branch point according to the present invention is raised. 3 (c) is a state diagram in which additional compressive stress is introduced to the lower casing concrete by lowering the branch point after the upper casing concrete is cured. Existing simple beam type preflection composite beam reduces the compressive stress introduced into the lower casing concrete by the preflection load while the lower casing concrete is cured under the prefraction load. do. Therefore, it is possible to compensate for the reduction of the compressive stress due to creep and dry shrinkage by raising and lowering the branch point in the center of the trunk. FIG. 4A shows the state of the pre-flection load using the branch point according to the present invention. It is the cross-sectional value after pouring and curing the lower casing concrete. Figure 4 (b) is a cross-sectional value for the final section in the simple beam-type preflex composite beam using the branch point. Figure 5 (a) is a 30m interval of the simple beam-type preflex composite beam using the branch point according to the present invention. The cross sectional view and the final stress diagram. FIG. 5B is a cross-sectional view and a stress diagram of a 30m section of a conventional simple beam preflex composite beam. 5 (a) is able to introduce additional compressive stress due to the rise and fall of the branch point can be designed with a smaller cross section than Figure 5 (b) and to reduce the amount of steel and concrete of the upper and lower flanges You can. In addition, while the tensile stress at the lower end of the lower casing concrete is 61.43 kg / cm ² of the conventional simple beam preflex composite beam, the simple beam preflex composite beam using the supporting point according to the present invention has a stress of 20.97 kg / cm ² . Can be reduced to about 30%. When comparing the steel amount and concrete amount of Figure 5 (a) and (b) is as follows. As shown in (a) of FIG. 5, the amount of steel of the simple beam preflex composite beam using the branch point according to the present invention is 586cm ² and the concrete amount is g300cm ² and the conventional simple beam preprex composite beam as shown in (b) of FIG. The amount of steel is 806cm ² and the amount of concrete is 10100cm ² , which can greatly reduce the amount of steel and concrete.

In the present invention, after placing and curing the lower casing concrete by loading the pre-fraction load, it is mounted between the shifts at the site and then the branch point is installed in the middle of the trunk to raise the branch point, and then after placing and curing the upper casing and the abdominal concrete. By lowering the branch point, it is a method that can additionally introduce compressive stress to the lower casing concrete.

Since the present invention can introduce additional compressive stress to the lower casing concrete using the branch point, the tensile stress at the lower end of the lower casing concrete generated by dead and live loads can be reduced to about 30% compared to the conventional one. It can greatly reduce the amount of steel and concrete in the quantity used.

An object of the present invention is to install a branch point in the middle of the ground to prevent the reduction of the compressive stress due to creep and dry shrinkage in the conventional simple beam preflex composite beams by raising and lowering to introduce additional compressive stress to creep and dry shrinkage The present invention provides a manufacturing method of a simple beam type preplex composite beam using branch points which can prevent the reduction of compressive stress and greatly reduce the amount of steel and concrete.

Claims (1)

In manufacturing the existing simple beam preflex composite beam, after reducing the initial stress due to creep and dry shrinkage, the branch point is set up in the middle of the bridge to raise and lower the branch after pouring and curing the upper casing concrete and abdominal concrete. By introducing additional compressive stress into the lower casing concrete, it is possible to significantly reduce the tensile stress occurring at the bottom of the lower casing concrete and to produce a simple beam-type preflex composite beam using branch points that can greatly reduce the amount of steel and concrete. Method.